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Multiple Reflections (multiple + reflection)
Selected AbstractsFast Inverse Reflector Design (FIRD)COMPUTER GRAPHICS FORUM, Issue 8 2009A. Mas I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism; I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling , Physically based modeling; I.3.1 [Hardware architecture]: Graphics processors Abstract This paper presents a new inverse reflector design method using a GPU-based computation of outgoing light distribution from reflectors. We propose a fast method to obtain the outgoing light distribution of a parametrized reflector, and then compare it with the desired illumination. The new method works completely in the GPU. We trace millions of rays using a hierarchical height-field representation of the reflector. Multiple reflections are taken into account. The parameters that define the reflector shape are optimized in an iterative procedure in order for the resulting light distribution to be as close as possible to the desired, user-provided one. We show that our method can calculate reflector lighting at least one order of magnitude faster than previous methods, even with millions of rays, complex geometries and light sources. [source] A coupled simulation of an explosion inside a lined cavity surrounded by a plastic compressible mediumINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2007V. R. Feldgun Abstract The paper develops a coupled approach to simulate an axisymmetric explosion inside a buried lined cavity. The approach allows accounting for all the stages of the process: detonation of the internal charge; the shock wave propagation in the internal gas with further interaction with the lining, including multiple reflections; soil,structure dynamic interaction, including multiple gap openings and closures and wave propagation in the surrounding compressible plastic medium. The interaction problem is solved by a combination of the variational difference method and of the modified Godunov's method based on the fixed Eulerian mesh with the so-called mixed cell. The contact pressures acting on the lining due to both detonation products and soil,lining interaction are computed through the solution of the joint system of finite difference equations of gas, shell and soil dynamics using a simple iteration method. Copyright © 2007 John Wiley & Sons, Ltd. [source] Ab initio study of the OH + CH2O reaction: The effect of the OH··OCH2 complex on the H-abstraction kineticsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2006Shucheng Xu Kinetics for the reaction of OH radical with CH2O has been studied by single-point calculations at the CCSD(T)/6-311+G(3df, 2p) level based on the geometries optimized at the B3LYP/6-311+G(3df, 2p) and CCSD/6-311++G(d,p) levels. The rate constant for the reaction has been computed in the temperature range 200,3000 K by variational transition state theory including the significant effect of the multiple reflections above the OH··OCH2 complex. The predicted results can be represented by the expressions k1 = 2.45 × 10 -21T2.98 exp (1750/T) cm3 mol,1 s,1 (200,400 K) and 3.22 × 10 -18T2.11 exp(849/T) cm3 mol,1 s,1 (400,3000 K) for the H-abstraction process and k2 = 1.05 × 10 -17T1.63 exp(,2156/T) cm3 mol,1 s,1 in the temperature range of 200,3000 K for the HO-addition process producing the OCH2OH radical. The predicted total rate constants (k1 + k2) can reproduce closely the recommended kinetic data for OH + CH2O over the entire range of temperature studied. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 322,326, 2006 [source] Light trapping in organic solar cellsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008Michael Niggemann Abstract One key problem in optimizing organic solar cells is to maximize the absorption of incident light and to keep the charge carrier transport paths as short as possible in order to minimize recombination losses during the charge carrier extraction. The large versatility of organic semiconductors and compositions requires specific optimization of each system. Due to the small thickness of the functional layers in the order of several ten nanometres, coherent optics has to be considered and therefore interference effects play a dominant role. Here we present and discuss concepts for light trapping in organic solar cells. These are wide gap layers in planar solar cells, folded solar cell architectures benefiting from the illumination under inclined incident angles and multiple reflections and absorptions as well as diffraction gratings embossed into the photoactive layer. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Realization of extreme light extraction efficiency for moth-eye LEDs on SiC substrate using high-reflection electrodePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Ryosuke Kawai Abstract The effect of a high-reflection electrode on the opposite side of a moth-eye structure on the performance of a nitride-based blue LED is described. Because of the interference effect enhanced by multiple reflections with a high-reflectance Ag-Pd-Cu alloy (APC) p-contact, light extraction is markedly improved. For the 600-nm-pitch sample, both APC and conventional Ni/Au contacts were used. Although the light output powers of LEDs with APC and Ni/Au p-contacts without moth-eye structure are almost the same, those with a moth-eye structure are markedly increased and differ from each other. For the APC contact, the light output is improved by a factor of 3.4, whereas that with a Ni/Au contact is increased by a factor of 2.2. In addition, we fabricated moth-eye LEDs with pitches of 300 nm, 400 nm, 500 nm and 600 nm by low-energy electron-beam projection lithography. We found that the sample with a pitch of 500 nm has the highest output power, which is 3.7 times higher than that of the reference sample. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultra-thin silicon solar cell: Modelling and characterisationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008L. Danos Abstract An ultra-thin crystalline silicon solar cell with an active silicon layer of 200 nm has been fabricated and fully characterised electrically (I-V characteristic, spectral response) and optically (Variable Angle Spectroscopic Ellipsometry). Interference effects were observed in the spectral response of the cell due to multiple reflections from the layers within the cell. A mathematical model was developed to account for the different reflections and transmission within the cell which reproduced excellently the essential features of the experimental spectral response. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Determination of linear birefringence of a multiple-order wave plate using a phase-sensitive ellipsometerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008H. C. Wei Abstract A phase-sensitive interferometric ellipsometer is setup in order to characterize linearly birefringent parameters (no,ne,m) of a multiple-order wave plate (MWP) precisely where no and ne are refractive indices of ordinary and extraordinary rays respectively while m is the number of the order of interference. In order to avoid multiple reflections in MWP during the phase retardation measurement at oblique incidence, two tilted phase retardations with respect to the oblique incident angle rotated along x-axis and y-axis are measured and then subtracted from each other. In the mean time, the spatial shifting effect of the emerging beams from MWP is reduced too. This results the accuracy of linear birefringence measurement. Finally, a multiple-order quartz wave plate was tested. The experimental results verify that the phase-sensitive interferometric ellipsometer is able to precisely measure linear birefringence and the order number of a MWP. In this measurement, the phase stability of the interferometric ellipsometer was 0.3°/hr. It implies the sensitivity on refractive index measurement at ,n , 10,6 was achieved in the experiment. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||